Gce Model Questions Vol1 2017 Geography Question 41

Region X is exposed to two types of natural hazard. A flood occurs on average once every 20 years and causes average damage of £120 million. An earthquake occurs on average once every 50 years and causes average damage of £300 million. The local authority can implement one of two mitigation measures: - A flood barrier costing £15 million, lasting 30 years, which reduces flood damage by 70 %. - An earthquake‑retrofit programme costing £25 million, lasting 30 years, which reduces earthquake damage by 60 %. Assuming the annualised cost of a measure is its total cost divided by 30 years and that the expected annual loss from a hazard equals its probability of occurrence multiplied by the (reduced) damage, which single mitigation measure gives the lower total expected annual cost (annualised mitigation cost plus expected annual loss)?